Ok so I went to Historian Symon (The NPC who gives you armor/weapons for AC dungeon). and looks to me like that all the weapons you have to be lvl 80 to use D:. This is the lowest level dungeon in terms of requirement, so does that mean all equipment from any dungeon requires lvl 80? Also I saw many copies of the same weapon on the menu? Is that just a bug?

If you're talking about what is available from dungeon vendors pre-80 then yes, it's only the rare quality armor that they sell.

The vendors are in Fort Marriner. When you talk to them and select the "Show me what armors you have." option it will pop up a window with two tabs (that are on the left side of the window). The first tab holds rare quality armor for the level of it's explorable mode. For example: AC vendor has rares that are level 35 that you can buy for tokens. The second tab has exotic quality armor for level 80s.

Each dungeon vendor will have 3 stat choices to choose from. For example: the AC vendor will have 3 stat choices for the armor and weapons they sell; Power/Toughness/Vitality, Precision/Vitality/Healing Power, Power/Precision/Condition Damage.